Using set_shader_param with a color returns non-linear colors

[nathanfranke]

Godot version: v3.1.stable.mono.official (LATEST)

OS/device including version: Ubuntu 18.04 bionic,
Kernel: x86_64 Linux 4.18.0-17-generic

Issue description:
If using colors to transfer values (Since sampler2d is our only array), The values seem to be offset by 0.05 and put through a square root function

If the red value is set to sqrt(0.55), the line seems to appear in the middle

Steps to reproduce:

• Use set_shader_param('param_name', Color(0.5, 1.0, 1.0)) to set a specific color
• When accessing the color in the shader, the values will be mutated

Minimal reproduction project:
GodotTestProject.zip

[clayjohn]

What does it look like on the shader side? Are you using hint_color?

[nathanfranke]

Shader:

shader_type spatial;
render_mode specular_disabled;

uniform vec4 param;

void fragment() {
	ROUGHNESS = 1.0;
	METALLIC = 0.0;
	SPECULAR = 0.0;
	
	ALBEDO = vec3(abs(param.x - UV.x) * 10.0);
}

I have not tried hint_color, but I won't be able to use it because my actual project uses sampler2D. I get the error "Color hint is for vec4 only"

[clayjohn]

Its because you are using a color. It looks like the engine is converting to sRGB for you because you are passing in a color instead of a vector. The problem goes away if you use a vector.

[nathanfranke]

If I were to pass in a Vector instead of a Color, how would I specify alpha? Godot does not have a Vector4 implementation.

As for hint_color, I am not able to use this flag since my main project uses a sampler2D and I need to pass a variable amount of data

[clayjohn]

Sampler2D won't have this problem as it is imported as linear by default unless you use hint_use_as_albedo

[Calinou]

As a workaround, is this allowed in the shader language? I haven't tried.

ALBEDO = vec3(abs(param.x - UV.x) * 10.0);
ALBEDO.a = 0.5;

[nathanfranke]

If I'm not mistaken, wouldn't this just make the mesh transparent? (If it had that flag enabled)

[nathanfranke]

As a workaround, you can convert all your data using this algorithm:
1.055 * pow(v, 1.0 / 2.4) - 0.055

Updated Test Project
GodotTestProject.zip

Neither "hint_color" nor "hint_albedo" fix the issue. Also, samplers do encounter this issue